AQP4 and systemic lupus erythematosus: Our study confirms weaker binding of NMO-IgG to full length AQP4, resulting in a lower sensitivity for clinically definite NMO (70%) and high risk NMO (39%) patients, besides also the M-23 IgG seropositive patient with SLE associated myelitis was negative for full length AQP4-IgG.